A transparent conductive film is used as a transparent electrode for liquid crystal displays or transparent touch panels or as an electromagnetic shielding material.
There are known transparent conductive films having indium oxide (In2O3), tin oxide (SnO2) or a mixed sintered material (ITO) of In2O3 and SnO2 which is formed on the surface of a transparent film made of polyethylene terephthalate (PET) or triacetyl cellulose (TAC) by a dry process such as vacuum deposition, sputtering or ion plating.
There are also known transparent conductive films obtained by a wet process in which a coating layer is formed by applying a conducting polymer to the surface of a transparent film. Polythiophene, polyaniline and polypyrrole are known as the conducting polymer used in the wet process.
Since the transparent conductive films are continuously processed in a web form, punched or surface processed and kept while they are bent, the transparent conductive films obtained by the dry process may crack while they are processed or kept, thereby increasing their surface resistances.
Meanwhile, the transparent conductive films formed by the wet process hardly crack because their coating layers have flexibility. Further, the wet process has such advantages that its production cost is lower than that of the dry process and it has high productivity as its coating speed is generally fast. However, the transparent conductive films formed by the wet process are not satisfactory in terms of conductivity and color.
Various improvements have recently been proposed for the transparent conductive films formed by the wet process. For example, a conducting polymer (Patent Document 1) comprising poly(3,4-dialkoxythiophene) and polyanion obtained by oxidation polymerizing 3,4-dialkoxythiophene in the presence of the polyanion has extremely low surface resistance while it retains a high light transmittance due to the improvement of its production process (Patent Document 2 and Patent Document 3).
However, a conductive film having a coating layer of the conducting polymer is inferior in moist heat resistance and is not suitable for use in liquid crystal displays (LCD) and transparent touch panels. Therefore, a method in which various binders are used to improve the water resistance of the conducting polymer has been proposed (Patent Document 4).    (Patent Document 1) JP-A 1-313521    (Patent Document 2) JP-A 2002-193972    (Patent Document 3) JP-A 2003-286336    (Patent Document 4) JP-A 2005-281704